TO-35 Spark Plugs

[AdamsTO35]

Setting up a TO-35 to do some brush hogging on 2-3 acres of land and snow plowing on a medium sized driveway in Ohio. I want to replace the spark plugs because they are either original or maybe even older then original. Currently there are AC86c spark plugs installed. I think they may be older then original because the manual lists 87c for Hot and 85c for standard replacements and it seems like 87c replaced 86c. Before I started to work on the tractor. It was not pinging but I have not put much load on it or ran it long. So I'm wondering if I should go with a hot plug or standard plug for my replacements. I seen posts about using Autolite 3116 as a replacement as well on this forum. Would this be a good plug for this work load?

 

[Steve@Advance]

Several considerations...

How's the general health of the engine? If it's an oil burner, go with the hotter plug. If it gets a lot of idling, cold starts without getting up to temp, a hotter plug will be less likely to foul or collect carbon soot.

If it's a good engine, and it will be subject to more heavy demand than idling or light use, go for a colder plug.

There is not a lot of difference in the heat range of those plugs. It's more of a "fine tuning" process for maximum plug life. If the timing is properly set, the centrifugal advance is working, the cooling system is working with a good thermostat, the mixture is right, it will work with any of the heat ranges. With today's E10 gasoline, and the low compression ratio of the engine, detonation is not a concern. If it clatters under load, most likely the ignition timing is too advanced.

As for the brand of plug, it's personal preference. I don't have any brand specific stories, good or bad.

 

[Tom H.]

Good reply Steve. Check your timing first I?ve never had any of my TO?s ping or knock under load. Here is a pic of the manual for the original plugs. I?ve never really been a brand purist, more which ones work and cost less. I?m happy with the champions

 

[JDEM]

Spark plug heat-range has nothing to do with the engine pinging or not. Not sure what your concern is. Heat range is mostly about keeping
the plug clean. If too cold it fouls up faster. If too hot, the porcelain insulator can get shorted under extreme conditions. For normal
medium load use like you are describing, likely you would never detect any difference with any of the heat ranges you cited.

 

[phil(va)]

I use 3116 AutoLites in TO30s and 35s and love them.